Indeed, hackers will leave footprints if they try to transfer funds from hacked account. More so to speak that they are targeting vulnerable funds; thus, susceptible for an attack.
However, most of these attacks were very successful that they can still managed to get btc and convert it into fiat. However, if there are individuals trying to hack, they would be very big and well funded. In addition, attacks through phising websites and application can be worth noting. Note that most hacks happened in huge markets like bitfinex, binance, huobi and etc. Recent event on twitter would not be considered a direct attack to btc, rather they are accumulating btc from scammed victims. Well, time will tell what made hackers do what they do. Are they trying to test the system of bitcoin or are they trying to proved something they are good about?